Long-term intravenous calcitriol in secondary hyperparathyroidism: the role of technetium-99m-MIBI scintigraphy in predicting the response to treatment

Failed Switching off in the MIBI-Parathyroid Scintigraphy in a Dialyzed Patient with Secondary Hyperparathyroidism Responsive to Cinacalcet Therapy

The aims of your case report is to show the predictivity of (99m)Tc-sestamibi (MIBI) scintigraphy and doppler ultrasound imaging on secondary hyperparathyroidism (SHPT) in a patient responsive to calcimimetic treatment. Moreover, it has been reported that calcimimetic has great potential in reducing the volume of the parathyroid gland. On the other hand, the MIBI scintigraphy is considered a crucial diagnostic procedure to monitor the response to therapy in terms of turnover and cellular metabolism; whereas, ultrasound to monitor the volume variation in response to treatment. It is described the case of a 73-year-old man on hemodialysis from 1995 for ESRD. Within 2 years the patient gradually developed SHPT with progressively increased iPTH up to 1,000 rhog/ml. The ultrasound, highlighted the presence of two parathyroid hyperplasia, confirmed by scintigraphy, showing focal increase uptake of sestamibi in the same anatomical areas. As a result of the patient's refusal to perform a parathyroidectomy, cinacalcet, was administered (65 mg overage daily dose). After a year of treatment, there was a striking decrease of iPTH (from 1300 to 57 rhog/ml, -95%); but, on the contrary to expectations, this positive metabolic outcome, was not followed by parathyroid changes in ultrasound and scintigraphic findings.

Medical therapy of secondary hyperparathyroidism in chronic kidney disease: old and new drugs

Secondary hyperparathyroidism (SHPT), a common complication of chronic kidney disease, is characterised by elevated serum levels of parathyroid hormone, parathyroid hyperplasia, excessive bone resorption and increased risk for cardiovascular morbidity. The stringent metabolic targets proposed by the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) for patients with SHPT are difficult to achieve using conventional treatment regimens. Several new agents, including new vitamin D sterols and phosphate binders, as well as a novel class of compounds--the calcimimetics--have been developed in recent years. This review examines new and traditional therapies for SHPT and how these can best be utilised in order to achieve the new K/DOQI targets.

The calcium-sensing receptor: a key factor in the pathogenesis of secondary hyperparathyroidism

Serum calcium levels are regulated by the action of parathyroid hormone (PTH). Major drivers of PTH hypersecretion and parathyroid cell proliferation are the hypocalcemia and hyperphosphatemia that develop in chronic kidney disease patients with secondary hyperparathyroidism (SHPT) as a result of low calcitriol levels and decreased kidney function. Increased PTH production in response to systemic hypocalcemia is mediated by the calcium-sensing receptor (CaR). Furthermore, as SHPT progresses, reduced expression of CaRs and vitamin D receptors (VDRs) in hyperplastic parathyroid glands may limit the ability of calcium and calcitriol to regulate PTH secretion. Current treatment for SHPT includes the administration of vitamin D sterols and phosphate binders. Treatment with vitamin D is initially effective, but efficacy often wanes with further disease progression. The actions of vitamin D sterols are undermined by reduced expression of VDRs in the parathyroid gland. Furthermore, the calcemic and phosphatemic actions of vitamin D mean that it has the potential to exacerbate abnormal mineral metabolism, resulting in the formation of vascular calcifications. Effective new treatments for SHPT that have a positive impact on mineral metabolism are clearly needed. Recent research shows that drugs that selectively target the CaR, calcimimetics, have the potential to meet these requirements.

Secondary hyperparathyroidism in chronic hemodialysis patients: prevalence and race

Secondary hyperparathyroidism is a common complication of renal failure. The exact prevalence in chronic hemodialysis patients in not known. We evaluated 122 patients who were receiving maintenance hemodialysis for at least 12 months in 2 dialysis centers in mid Michigan. Seventy-eight percent of the patients had iPTH above 200 pg/mL (mean 481 pg/mL), 19% had iPTH within the accepted normal range (mean 155 pg/mL), while 3% had level below 100 (mean 53 pg/mL). Phosphate, calcium, calcium phosphate product, age and time on dialysis are the important factors correlating with elevated iPTH. There was no significant difference in iPTH between diabetic and nondiabetic patients with mean iPTH of 403 pg/mL and 407 pg/mL respectively. Black patients had a statistically significant elevated iPTH compared with white patients with a mean iPTH of 438 pg/mL and 283 pg/mL respectively (p < or = 0.004). Factors that predict the response to vitamin D therapy need to be evaluated to help reduce the high prevalence of secondary hyperparathyroidism. The patterns of bone disease in black patients need to be evaluated to further define the accepted normal iPTH range for this population.